Magnetic deflection amplifier utilizing both positive and negative voltage supplies for high-speed deflection

ABSTRACT

A magnetic deflection amplifier of the type employing a single deflection coil for controlling the movement of a cathode-ray tube beam along one coordinate axis includes both positive and negative low-voltage supplies connected to supply the energy to move the beam for a majority of the operating time, and positive and negative high-voltage supplies to move the beam rapidly and/or through large deflection distances when needed. One form of high-voltage supply includes an inductor having an inductance several times the inductance of the deflection coil to supply the energy necessary to change the current through the deflection coil rapidly in the desired direction.

United States Patent m1 3,628,083

[72] Inventors Richard E. Holmes 3,155,873 1 H1964 Paschal 3 [5/27 Bellbrook; 3,426,245 2/ l 969 Yurasek 315/27 Joe A. Mays, Xenia, both of Ohio 3,337,767 8/ l 967 Montrichard 315/26 [21] P 847875 Primary Examiner- Rodney D. Bennett, Jr.

22 Filed Aug. 6, 1969 Asst-m E J M P [451 Paiemed 1971 mom: a 6 l F h & B

[73] Assignee Systems Research Laboratories, Inc. y e renc ugg Montgomery County, Ohio [54] MAGNETIC DEFLECTION AMPLIFIER UTILIZING BOTH POSITIVE AND NEGATIVE VOLTAGE SUPPLIES FOR HIGH-SPEED DEFLECTION ABSTRACT: A magnetic deflection amplifier of the type employing a single deflection coil for controlling the movement of a cathode-ray tube beam along one coordinate axis includes 7 Claims, 5 Drawing Figs.

both positive and negative low-voltage supplles connected to 315/27 TD supply the energy to move the beam for a majority of the 1 29/70 operating time, and positive and negative high-voltage sup- [50] Field oi Search 3 i5/27 TD, plies to move the beam tapidly and/or through large d fl 27 27 LC distances when needed. One form of high-voltage supply includes an inductor having an inductance several times the in- [56] Rekrenccs cued ductance of the deflection coil to supply the energy necessary UNITED STATES PATENTS to change the current through the deflection coil rapidly in the 3,426,24l 2/l969 Perkins 315/27 desired direction.

I5 ls m ,2: L-Wvawn-cu L 1 LOW H men Ry 3 Sheets-Sheet 1 FIG-1 HIGH LOW

SWITCH HIGH LOW FIG-3 INVENTORS a v! m m M 0 L T 0 M E M M H mu R v! 5 Patented Dec. 14, 1971 3 Sheets-Sheet H u 3% 71 :o tmm 21: :E u :3 w Lr|||L I I l I I l l l I I I l l l|| Patented Dec. 14, 1971 3 Sheets-Sheet 3 ON OP mp vmo n wOmDOm MAGNETIC DEFLEC'IION AMPLIFIER UTILIZING BOTH POSITIVE AND NEGATIVE VOLTAGE SUPPLIES FOR HIGH-SPEED DEFLECT ION BACKGROUND OF THE INVENTION Since magnetic deflection coils used to position the beam of cathode ray tubes are inductors, relatively large power supply voltages are required to change the current flow rapidly. These large voltages, however, will result in a proportionately large power dissipation in the controlling amplifier even though a larger voltage is not required for a majority of the operating time. It is when rapid deflections are desired that a high-voltage supply to the deflection coil will be desired.

It would be desirable therefore to provide means to supply the deflection coil from a lower voltage power supply during a major portion of the operating time, thus reducing the power dissipation in the circuit, but also to apply a substantially higher voltage during those periods when large and/or rapid beam deflections are required. Several attempts have been made to accomplish this. as illustrated in US. Pat. Nos. 3,337,767 and 3,378,720. These patents show a first or low voltage source applied to a deflection coil, and a switching circuit responsive to the voltage on the coil to connect momentarily a higher voltage source which thereby supplies the additional power needed to move the beam of a cathode-ray tube rapidly from one position to another.

SUMMARY OF THE INVENTION This invention relates to an improved magnetic deflection amplifier for use principally with a single deflection coil for positioning a cathode-ray tube beam along one coordinate axis. Since only a single deflection coil is employed, problems of symmetry often encountered when using deflection coils connected in a push-pull arrangement are avoided. Both positive and negative low voltage sources are provided to supply the current to the deflection coil to deflect the beam to either side of a center. quiescent position, and both positive and negative high-voltage sources are provided when rapid beam deflections are called for by the input signal to the amplifier.

The step response time for a direct coupled magnetic deflection amplifier is proportional to the inductance of the deflection yoke and the magnitude of the current change required and is inversely proportional to the voltage available across the deflection coil. The power dissipation of the circuit is, of course, the product of the current and the voltage. Thus, the larger the power supply voltage, the smaller the step response time and the larger the power dissipation.

The present invention utilizes low and high-voltage sources controlled by a switch. When the input signal requires a step response time smaller than that which can be provided by the lower voltage power supply, a voltage comparator will switch the higher voltage power supply into operation. Of course, means are provided to isolate and protect the low voltage supply from the high voltage supply during the switching operation. This results in a shorter step response time, when required, while at the same time reducing the total power consumption since the higher voltage power supply is only used when needed.

In one embodiment of the invention, capacitors in positive and negative high-voltage sources store suflicient energy to move the beam quickly through the largest required deflection. In another embodiment of the invention, inductors are connected to supply the additional energy needed to move the beam rapidly.

One embodiment of the invention utilized an inductor connected in parallel with the low voltage supply. A transistor in series with the inductor causes current to flow therethrough during periods when the capacity of the low-voltage supply to provide adequate deflection current is not exceeded. When a high voltage is required to change the current through the deflection coil, this transistor is gated into its nonconducting state, and the energy stored in the inductor is then routed through an isolating diode to the deflection coil.

In still another embodiment of the invention, an inductor is placed directly in series with the deflection coil. A constant current supply controls the current flow through the inductor, and an operational amplifier controls the current through both the inductor and the deflection coil. When a large deflection current is required, such as during retracing, the entire energy stored in the inductor will be available to change the current through the deflection coil.

Thus, this invention utilizes an operational amplifier for controlling the current to a single magnetic deflection coil and, in one embodiment, employs both positive and negative voltage supplies to provide the necessary current to move the cathode ray tube beam rapidly. The high-voltage source may be provided by the energy stored in inductors connected to the deflection coil.

It is therefore an object of this invention to provide an improved magnetic deflection amplifier of the type described for use in supplying controlled currents to a single deflection coil for the purpose of positioning a cathode ray tube beam along one coordinate axis wherein positive and negative low voltage supplies are provided to minimize power dissipation during a major portion of the operation of the circuit and wherein positive and negative high voltage supplies are provided when rapid beam deflections are required and to provide a magnetic deflection circuit of the type described employing inductors to store the energy required to change the current through the deflection coil when necessary to deflect the beam rapidly, as required by the operation of the circuit.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and then appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the components which comprise one embodiment of the invention wherein both positive and negative low and high-voltage sources are provided;

FIG. 2 is a detailed electrical schematic diagram of one embodiment of the invention;

FIG. 3 is an electrical schematical diagram showing the use of an inductor to provide the high voltage necessary to move the beam quickly from one position to another;

FIG. 4 is a block diagram of another embodiment of the invention;

FIG. 5 is a detailed schematic electrical diagram of the embodiment shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is now made to FIG. 1 which is a block diagram showing one form of the invention. A single deflection coil Ly is placed around the neck of a cathode ray tube 10 and controls the deflection of the electron beam within the tube along one coordinate axis. The current through the deflection coil Ly is supplied by an operational amplifier l5, and the input to the operational amplifier from control circuits, not shown, is applied at terminal 16 and through resistor R1. A feedback voltage to the operational amplifier is provided by resistor R2 which is in series with the deflection coil Ly. This feedback voltage is proportional to the current through the deflection coil. Resistor Ry represents the resistance of the deflection coil. The feedback voltage is applied to the input of the operational amplifier through resistor R3.

In the embodiment shown, a single deflection coil is employed to move the beam of the cathode ray tube along one coordinate axis. Accordingly, both positive and negative voltage supplies are required to deflect the beam from either side of a center, quiescent position. As shown in the block diagram, both positive and negative low-voltage supplies 20 and 21, respectively, are connected to deflection coil Ly through switch 25. When necessary to move the beam to the right, for example, the positive low-voltage supply 20 will be utilized, and when the beam is moved to the left, the negative low-voltage supply 21 will be employed. Both the positive and negative low voltage supplies have sufficient current capacity to position the beam to the outermost limits along the coordinate axis being controlled.

Both positive and negative high voltage supplies 27 and 28, respectively, are also provided when it is desired to move the beam of the cathode-ray tube rapidly. The switch 25 senses the voltage on the deflection coil Ly, and when the voltage approaches the voltage of the low-voltage supplies 20 or 21, the appropriate high voltage supply 27 or 28 will then be connected to the operational amplifier to provide the extra voltage needed to change the current through the deflection coil rapidly.

After the beam has moved to the desired position, the voltage necessary to change the current through the deflection coil will decrease, and the switch 25 will then open and return the circuit to its original condition where the positive and negative low-voltage supplies provide the necessary current to maintain the beam at a desired position. Thus, the positive and negative high voltage supplies are only connected to the deflection coil when the current therethrough is to be changed rapidly and/or through large magnitudes, thus minimizing dissipation in the entire circuit.

The degree of improvement of this type of system over one where only a high-voltage supply is used will depend, of course, on the ratio of the magnitude of the highand low voltage supplies and upon the amount of time the high-voltage supply is connected in the circuit. in other words, if the highvoltage supply is only connected in the circuit for short periods of time, the system described above will dissipate less total power.

The step response time is given as follows:

t is the step response time Ly is the deflection coil inductance Al is the required current change E is the absolute value of the positive and negative power supplies R is the sum of the deflection coil resistance Ry and the sense resistor R2 and E,is the element drop across the saturated nonlinear element in the output stage.

The table below compares the desired response time (A!) with the actual response times available for two types of amplifiers, one having low-voltage power supplies (1E) and the other having both highand low-voltage power supplies (:E1, ':E2), as described above.

'IAB LE I Actual A t Desired Improved ezALyAl It Standard amplifier at Al (Ly=tamplifier El=i10 v. sec. amp. Al/At henry) E= :10 v. E2=:l:70 v.

10 10 1O 10 10' 10- 10- 10 10 10 10- 10- 7X10 10 1 413x10 1. 43 7X10- 7)(10' Xl0- l0 2X10 2 5X10- 5X10- 3X10 3. 3X 10 3. 3 3X10- 3X10- 1X10' l0 1 10 1X10 1X10- 7X10- l0 1 435x10 14. 3 10- 7X10" 5X10 10 2X10 10- 5X10- 3X10' l0 3.3X10 33 10- 3Xl0' 1 4s 1o- 10 7x10 70 10- 1 43x1o 1X10- 10 10X10 100 10- 1 43X10' As shown in the table, a current change (Al) of 10 amperes is desired in all of the examples shown. The response time (actual A! of the amplifier is limited to that value when the induced voltage (e across the deflection coil Ly equals the voltage of the power supply (E). When using only a low voltage power supply of IO volts, the shortest response time of the amplifier is 1X10 whereas when using a higher voltage power supply, the response time may be decreased to l.43X10seconds.

FIG. 2 shows a detailed electrical schematic diagram of one embodiment of the invention. Since the circuit is designed to supply both positive and negative voltages to a single deflection coil, both positive and negative power supplies and control circuits are provided. In FIG. 2, the operational amplifier 15 includes a preamplifier circuit comprising transistors Q1 through Q6, and a switching and current amplifier circuit including transistors Q7 through Q12. The input to the operational amplifier is applied on terminal 16 and through resistor R1 to resistor 03. An additional input may be applied on terminal 29 to the base of transistor Q1 for the purpose of establishing a reference to which the remainder of the circuit relates. The output from the switching and current amplifier circuit is applied to the deflection coil Ly, shown in the center of the diagram, and a feedback voltage across the sensing resistor R2 is applied to the input transistor Q3 through resistor R3.

A source of positive low voltage 20 and a negative low voltage 21 is provided through the switching and current amplifying circuit during most of the operating cycle. However, a positive high-voltage supply 27 and negative high-voltage supply 28 is provided during those intervals when rapid current changes through the deflection coil are required.

When the voltage on the deflection coil Ly approaches the voltage supplied by either the low-voltage sources 20 or 21, thus indicating maximum utilization of those power sources, this condition is sensed by either transistors Q13 or 017. The voltage established on the base elements of transistors Q14 or Q18 by the voltage-dividing network including resistors R4, R5 or R6, R7 will detennine the voltage when either transistors Q13 or Q17 conducts.

It is understood that the circuit 31 including transistors Q13 and 016 is used when the voltage on the deflection coil Ly is positive, and the circuit 32 including the transistors Q17 through Q20 is used when the voltage on the deflection soil Ly is negative.

When voltage on deflection coil Ly exceeds a predetermined voltage, as determined by the ratio of resistors R4 and R5, transistor Q13 conducts and gates transistors Q15 and Q16 into the conducting state. At this time, the positive high voltage supply 27, including capacitor C1, will be applied through transistor O9 to the deflection coil Ly. Diode D1 isolates the low-voltage supply 20 from the high voltage supply during the time when transistor Q16 is in the conducting state.

Similarly, if the magnitude of the negative voltage on the deflection coil Ly exceeds a predetermined magnitude, as determined by the voltage on the base of Q18 by the ratio of resistors R6 and R7, transistors Q19 and Q20 will conduct and connect the negative highvoltage supply 28, including capacitor C2, to the deflection coil through switching transistor Q12.

Thus, transistors Q13 through Q16 and Q17 through Q20 act as switch means responsive to the voltage output of the operational amplifier to connect a source of high voltage through the operational amplifier to the deflection coil whenever the magnitude of the voltage on the deflection coil exceeds a predetermined value, thereby providing additional voltage so that the current through the deflection coil can change more rapidly and thus position the cathode ray tube beam quicker than if only a single low-voltage supply were provided.

FIG. 3 shows another circuit for providing high voltage of the defection coil Ly. The circuit as shown in FIG. 3 may replace the circuit 31 of FIG. 2, or the circuit 32 of FIG. 2 with appropriate change in the polarity of the transistors, diodes and input voltages. The circuit of F IG. 3 employs a switching circuit including transistors Q13 and Q14, control transistor Q15 and a switching transistor Q16.

During these periods of the operating cycle when only a low voltage is required, the low voltage supply 20 will provide power to the deflection coil Ly through diode D1 and transistor Q9. Transistor Q16 is normally in the conducting state and therefore current from a suitable power source flows through resistor R8 and inductor L1 to ground through the low resistance path provided by transistor Q16. The inductor L2 is selected so that its inductance is approximately ten times the inductance of the deflection coil Ly.

When the voltage on the deflection coil Ly exceeds a predetermined magnitude. as determined by the resistors R4 and R5. transistor Q16 will be gated into the nonconducting state, and the energy stored in inductor Ll will be transferred through D3. and transistor O9 to the deflection coil Ly and will develop a voltage across the deflection coil sufficient to cause a current change in the proper direction. It will be apparent to those skilled in the art that the circuit can be modified to provide a negative high voltage when the magnitude of the negative voltage on the deflection coil Ly exceeds a predetermined value, usually approaching the capacity of the low voltage power source.

Another embodiment of the invention is shown in block diagram in FIG. 4 and the detailed schematic diagram in FIG. 5. In this embodiment, an operational amplifier receives an input signal through resistor R9. The output of the operational amplifier is applied to a shunt regulator 35 and through a switch to the deflection coil Ly. A feedback voltage is developed across resistor R10 and fed back to the input of the operational amplifier through resistor R1 I.

A constant current source 40 is also connected to the deflection coil Ly and supplies current of constant magnitude which is divided between the deflection coil and the shunt regulator. In the embodiment shown, the deflection coil is supplied with a negative voltage through the shunt regulator and the constant current source supplies positive voltage to the deflection coil. This arrangement permits the cathode ray tube beam to be moved relatively slowly in one direction along one coordinate axis of the tube and to be returned quickly in the opposite direction along that same coordinate axis.

In FIG. 5. the operational amplifier includes transistors 02 I. 022 and Q23. The emitter electrodes of transistors Q21 and Q22 are connected to a constant current source which includes transistor 024. The output of the operational amplifier is applied to the shunt regulator 35. including transistors Q25 and Q26.

Transistors Q21 and Q22 are operated as a differential amplifier with the input being applied to resistors R9 and R12. Transistor Q23 is a voltage amplifier having a gain of about 20. The shunt regulator 35. including power amplifier transistors Q25 and Q26, provides the high current gain necessary to drive the deflection coil. These transistors, however, cannot withstand the high voltages required for rapid retracting. so a switching circuit 25". including transistor Q27, is included to provide the necessary isolation.

The constant current source includes current regulating transistors Q28 and Q29 which establish a current level of approximately 7 amperes through inductor L2 which has an inductance ideally greater than 10 times the inductance of the deflection coil Ly. A positive going input to the operational amplifier [5" will cause transistors O21. Q23, and 025 through 027 to conduct heavily and result in a negative going waveform of equal magnitude across the sensing resistor 10. If the input to the amplifier goes negative rapidly. these transistors are turned off since the voltage across the sensing resistor R10 is not sufficient to cause the base current at O2! to be reduced to zero as required for operational amplifier operation. Under these conditions. the constant current source 40 will transfer the energy stored in inductor L2 through the deflection Ly until such time as the 021 base current requirements are met. This has the result of raising the voltage on the deflection coil Ly and the collector of transistor Q27. and transistor Q27 will go into the nonconducting state to protect the transistors in the shunt regulator 35.

This circuit therefore provides feedback which permits the current through the deflection coil to follow complex waveforms very precisely and provided the high voltages and currents to the deflection coil which are necessary for rapid retracting. The power transistors Q25 and Q26 operated near saturation during scan in one direction and are cut off during the high-voltage retrace.

The following component values were used in preferred embodiments as shown in the drawings.

RI. 3. I4. 14. 44. 45. K ohm R2 0.5 ohm R4. R6 320 ohm R5. 7.9. II. [2. l3 lllKohm R8 0.5 ohm RIO. Z9. 30. 50. II (LI ohm RIB. I7. 20. 12 680 ohm RI6. I9. 38. 43 33 ohm RIB. 2|. III. 36. 37. 40. 41. 52. 53 I00 ohm R23 8.2 K ohm R25. 33. 53 47 ohm R26. 32 I20 ohm R27. 3|. 47 22 ohm R34. 4| 6.8 K ohm R35. 39 390 ohm R46 470 ohm R48. 49 330 ohm Ly 0.1 mh. l.l. L2 20 mh. 0|. 1 MD 2369 Q3. 4 MD 5000 ()5. I0 2N 3931 Q 7 IN 3440 ()8 IN 4999 Q9 2N 37I6 O" IN 3879 QIZ 2N 3792 QIJ. I9 4036i (RCA) QIJ IN 3642 QIS. I7 40362 (RCA) Q16 2N 3879 QIII IN 3645 010 IN 4999 QZI. Z2 2N 3642 023 2N 5416 024 CL4720 015 IN 3379 016 SDT 8045 017 SDT 8805 028 2N 3055 Q2 2N 374l CI. 1 I L000 f ca. 4, l0. ll lpf cs. 8. 9 0.01, cs. 7. l2. l3 0.03 r CI-l. I5 8200 pl DI. Z. 3 IN I200 D4.5.6.7.8.IZ. I3 IN 9I4 DID. II IN 4001 D13. l4. l5 TID 4| 2|. 2 56VZ Z3 IN 472K Thus, an improved deflection amplifier has been described utilizing a single deflection coil to control the beam of a cathode-ray tube along one coordinate axis. Both positive and negative highand low-voltage sources are provided to reduce power consumption while at the same time permitting rapid movement of the beam when necessary. One form of highvoltage source includes an inductance several times greater than the inductance of the deflection coil to provide the necessary energy when needed to change the current to the deflection coil rapidly in the desired direction.

While the forms of apparatus herein described constitute preferred embodiments of the invention. it is to be understood that the invention is not limited to these precise forms of apparatus. and that changes may be made therein without departing from the scope of the invention.

What is claimed is: l. A deflection system for a cathode-ray tube employing a single magnetic deflection coil to position the beam of the cathode-ray tube along one coordinate. the combination comprising an operational amplifier having its input connected to receive signals for positioning the cathode-ray tube beam along said one coordinate, the output of said operational amplifier supplying current to said deflection coil;

feedback means for providing a voltage representative of the current through said deflection coil to the input of said operational amplifier;

a first source of voltage supplying current to said deflection coil through said operational amplifier;

an inductance for supplying a second higher source of voltage to said deflection coil through said operational amplifier; switch means for causing said inductance to supply said higher voltage when the output of said operational amplifier obtains a predetermined value thus providing an additional source of current to said deflection coil to move said beam quickly to a desired position on said cathoderay tube face. 2. The deflection circuit of claim 1 wherein said inductance is connected in parallel with said first source of voltage;

said circuit further including means for providing a low-resistance path through which current from said inductance may pass during periods when the output from said operational amplifier is below said predetermined value. said means opening said low-resistance path under control of said switch means when the output of said operational amplifier obtains said predetermined value thereby allowing the energy stored in said inductance to be transferred to said deflection coil thus to move the cathode-ray tube beam quickly to a desired position. 3. The deflection circuit of claim I wherein said inductance is connected in series with said deflection coil;

constant current means in series with said inductance; said operational amplifier controlling the current flow through said deflection coil in one direction by varying the combined current from said coil and said inductance; said inductance providing a high voltage across said deflection coil to cause current to flow in the opposite direction under control of said switch means when the output of said operational amplifier obtains a predetermined value. 4. A cathode-ray deflection circuit of the type employing a single magnetic deflection coil to position a cathode-ray tube beam along one coordinate, the combination comprising an operational amplifier having its input connected to a voltage source which controls the position of the cathoderay tube beam. the output of said operational amplifier connected to supply current through said deflection coil; feedback means for providing a voltage representative of the current through said deflection coil to the input of said operational amplifier; a first source of positive voltage connected to said deflection coil through said operational amplifier; a second source of positive voltage. greater in magnitude than said first source; first switch means responsive to the voltage output from said operational amplifier for connecting said second source of positive voltage to said operational amplifier whenever the positive magnitude of the output voltage of said operational amplifier exceeds a predetermined value; a first source of negative voltage connected to said deflection coil through said operational amplifier;

a second source of negative voltage, greater in magnitude that said first source of negative voltage; and

second switch means responsive to the output from said operational amplifier for connecting said second source of negative voltage to said operational amplifier whenever the negative magnitude of the output voltage of said operational amplifier exceeds a predetermined value.

5. The deflection circuit of claim 4 wherein said second source of positive voltage and said second source of negative voltage each includes an inductor connected in parallel thereacross;

said circuit further including means for providing a low-resistance path through which current from said inductor may pass. said means opening said low-resistance path under control of said first switch means and second switch means when the output from said operational amplifier obtains said predetermined value and thereby allowing the energy stored in one of said inductors to be transferred to said deflection coil thus to move the cathode-ray tube beam quickly to a desired position.

6. A deflection circuit for a cathode-ray tube including a single deflection coil for positioning the beam of the cathode-ray tube along one coordinate axis;

an operational amplifier having its input connected to receive signals for positioning the beam along said one coordinate;

feedback means for providing a voltage representative of the current through said deflection coil to the input of said operational amplifier;

a current supply having a first polarity;

a shunt regulator in series between said current supply and said deflection coil, said shunt regulator connected to the output of said operational amplifier thereby to control the current through said deflection coil and thus position the beam;

a second current supply having a polarity opposite from the polarity of said first supply;

an inductor connected to said deflection coil;

and constant current means between said second current supply and said inductor for providing a constant current through said inductor, said current being divided between said deflection coil and said shunt regulator the energy in said inductor supplying sufficient voltage to said deflection coil to cause rapid change in current in said deflection coil.

7. The circuit of claim 6 further including switch means in series between said deflection coil and said shunt regulator;

said switch means being biased to open and thus permit the energy in said inductor to be transferred to said deflection coil when the required current change through said deflection coil cannot be supplied by said shunt regulator.

Docket 5107 "0-1050 UNITED STATES KATENT OEFMZE CERTIFXCATE Oil CQRREQ HUN Patent NO. Dated l4, Invmflwr Richard E. Holmes and Joe A. Mavs It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 32, change "then" to the m line 74, insert to be following "beam". Column 3, line 22, insert the power following "minimizing"; line 75, change "10'" to l0" Column 4, line 10, change "resistor" to transistor line 36, change "soil" to coil line 63, change "of" to to line 70, change "these" to those Column 5, line 8, insert diode after "through";

lines 47-48, change "retracking" to retracing line 64, insert coil following "deflection"; line 71, change "provided" to provides line 73, change "retracking" to retracing Signed and sealed this 22nd day of August 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR' ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. A deflection system for a cathode-ray tube employing a single magnetic deflection coil to position the beam of the cathode-ray tube along one coordinate, the combination comprising an operational amplifier havinG its input connected to receive signals for positioning the cathode-ray tube beam along said one coordinate, the output of said operational amplifier supplying current to said deflection coil; feedback means for providing a voltage representative of the current through said deflection coil to the input of said operational amplifier; a first source of voltage supplying current to said deflection coil through said operational amplifier; an inductance for supplying a second higher source of voltage to said deflection coil through said operational amplifier; switch means for causing said inductance to supply said higher voltage when the output of said operational amplifier obtains a predetermined value thus providing an additional source of current to said deflection coil to move said beam quickly to a desired position on said cathode-ray tube face.
 2. The deflection circuit of claim 1 wherein said inductance is connected in parallel with said first source of voltage; said circuit further including means for providing a low-resistance path through which current from said inductance may pass during periods when the output from said operational amplifier is below said predetermined value, said means opening said low-resistance path under control of said switch means when the output of said operational amplifier obtains said predetermined value thereby allowing the energy stored in said inductance to be transferred to said deflection coil thus to move the cathode-ray tube beam quickly to a desired position.
 3. The deflection circuit of claim 1 wherein said inductance is connected in series with said deflection coil; constant current means in series with said inductance; said operational amplifier controlling the current flow through said deflection coil in one direction by varying the combined current from said coil and said inductance; said inductance providing a high voltage across said deflection coil to cause current to flow in the opposite direction under control of said switch means when the output of said operational amplifier obtains a predetermined value.
 4. A cathode-ray deflection circuit of the type employing a single magnetic deflection coil to position a cathode-ray tube beam along one coordinate, the combination comprising an operational amplifier having its input connected to a voltage source which controls the position of the cathode-ray tube beam, the output of said operational amplifier connected to supply current through said deflection coil; feedback means for providing a voltage representative of the current through said deflection coil to the input of said operational amplifier; a first source of positive voltage connected to said deflection coil through said operational amplifier; a second source of positive voltage, greater in magnitude than said first source; first switch means responsive to the voltage output from said operational amplifier for connecting said second source of positive voltage to said operational amplifier whenever the positive magnitude of the output voltage of said operational amplifier exceeds a predetermined value; a first source of negative voltage connected to said deflection coil through said operational amplifier; a second source of negative voltage, greater in magnitude than said first source of negative voltage; and second switch means responsive to the output from said operational amplifier for connecting said second source of negative voltage to said operational amplifier whenever the negative magnitude of the output voltage of said operational amplifier exceeds a predetermined value.
 5. The deflection circuit of claim 4 wherein said second source of positive voltage and said second source of negative voltage each includes an inductor connected in parallel thereacross; said circuit further including means for providing a low-resistance path through which current from said inductor may pass, said means opening said low-resistance pAth under control of said first switch means and second switch means when the output from said operational amplifier obtains said predetermined value thereby allowing the energy stored in one of said inductors to be transferred to said deflection coil thus to move the cathode-ray tube beam quickly to a desired position.
 6. A deflection circuit for a cathode-ray tube including a single deflection coil for positioning the beam of the cathode-ray tube along one coordinate axis; an operational amplifier having its input connected to receive signals for positioning the beam along said one coordinate; feedback means for providing a voltage representative of the current through said deflection coil to the input of said operational amplifier; a current supply having a first polarity; a shunt regulator in series between said current supply and said deflection coil, said shunt regulator connected to the output of said operational amplifier thereby to control the current through said deflection coil and thus position the beam; a second current supply having a polarity opposite from the polarity of said first supply; an inductor connected to said deflection coil; and constant current means between said second current supply and said inductor for providing a constant current through said inductor, said current being divided between said deflection coil and said shunt regulator, the energy in said inductor supplying sufficient voltage to said deflection coil to cause rapid change in current in said deflection coil.
 7. The circuit of claim 6 further including switch means in series between said deflection coil and said shunt regulator; said switch means being biased to open and thus permit the energy in said inductor to be transferred to said deflection coil when the required current change through said deflection coil cannot be supplied by said shunt regulator. 